There are plenty of words in Japanese that are difficult to translate directly into English. This is one of the challenges of early efforts to learn Japanese. It doesn’t help either when these terms are clumsily translated and taught as having a certain fixed meaning that doesn’t even make sense in similar situations in English.
A good example of such words, are the often confused terms ‘otsukaresama’ (お疲れ様) and ‘gokurosama’ (ご苦労様). Taken literally, otsukaresama can be translated to mean ‘a tired person’, and gokurosama could be translated to mean ‘a hard worker’. But that really doesn’t help much. because in English we don’t often go up to random co-workers, for example, and tell them that they are ‘a tired person’.
In many ways, these two terms are used in a similar way, and they can sometimes be confusing. They are both used most often as a means of expressing gratitude or acknowledgement of co-workers, or people that have done something for you. They can also be used as a generic way of greeting or saying goodbye to co-workers in an office situation. In these situations, it is most common to use the term otsukaresama’, or the slightly more formal ‘otsukaresama deshita’.
In general, otsukaresama is used between coworkers or to people of the same or higher social level or standing, and gokurosama is used particularly when thanking or acknowledging someone in a subordinate position, whether it be a subordinate worker in your office, or someone that has just done some task for you. One Japanese blog suggests that even more important than the social standing is the degree to which the other person has put themselves into a task that brought you profit or benefit. Where there has been a great deal of effort spent on your behalf, it is customary to thank the person by saying ‘gokurosama desu’. However, this is generally still not used for people of a higher standing, such as your boss etc – in this case ‘otsukaresama’ is still the best term to use.
If you are simply acknowledging a co-worker or acquaintance, or a friend in the regular course of both of your activities, and where no particular effort has been spent on your behalf by the other person, ‘otsukaresama’ is very commonly used. In this sense then, ‘gokurosama (desu/deshita)’ really takes on a meaning akin to ‘thank you very much’, whereas ‘otsukaresama (desu/deshita)’ may be best translated as simply ‘thanks’. These definitions may not fit all circumstances, but they can be a good guide for when to use which term.
Alternatively, when you want to thank someone for something that they have done for you, you could always just say ‘arigato (gozaimasu/gozaimashita)’, or ‘thank you’. But then, that would be too simple… In addition to offering expressions of thanks or acknowledgement, these terms are also used as greetings, particularly in an office or school environment. In such a setting you will hear ‘otsukaresama’ a lot, especially when someone leaves the office for the day. As a side note, when arriving at the office for the day, it is typical to greet your colleagues by saying ‘ohayo gozaimasu’. This can be used any time in the morning, especially when greeting someone for the first time that day. If you happen to arrive at the office later in the day, or return from spending some time out of the office, you may be greeted by ‘otsukaresama’ instead, with the assumption being that you have been about some other work before arriving at the office (little do they know….. 
).
Don’t feel bad if you confuse these two terms, especially when leaving the office. In a national 2005 Agency for Cultural Affairs survey, it was discovered that when leaving the office, 70% of Japanese people use the term ‘otsukaresama (deshita)’, while 15% say ‘gokurosama (deshita)’, and another 11% just say ‘arigato (gozaimashita)’, or ‘thank you (very much)’… 1% say domo….
If you have finished reading this long winded and utterly confusing explanation, all there is left to say is…. gokurosama deshita….er…. otsukaresama deshita…. er…..
